Section I: FGIDs: Background InformationPhysiologyFundamentals of Neurogastroenterology: Physiology/Motility – Sensation
Section snippets
Normal Physiology: Main Components
The fundamental gastrointestinal functions include sensation, motility, digestion, absorption, and secretion.
Food, Meal Intake, and Microbiota
The meal ingested is transformed from the mouth to the ileum, first by digestion and then by absorption, so that only nonabsorbed residues pass into the colon. The whole digestive–absorptive process down to the terminal ileum is finely regulated depending on the composition of intraluminal content; nutrients in the stomach and small bowel have limited effects on colonic activity. Nonabsorbed meal residues entering the colon serve as substrate to feed microbiota and this interaction has several
Genetics
Genetic mechanisms appear to be associated with visceral pain and motor functions in health and functional gastrointestinal disorders. Familial aggregation and twin studies support a genetic factor in IBS. In addition, gene variations have been described in association with the symptom phenotype of IBS, biomarkers of visceral pain, and motor function.
Esophageal motility and lower esophageal sphincter function
The coordinated motor pattern of the esophagus initiated by the act of swallowing is called primary peristalsis. Primary peristalsis usually clears most contents of the esophagus into the stomach. Secondary peristalsis is provoked by residual food or reflux events, and it is not accompanied by pharyngeal contraction or upper esophageal sphincter relaxation. Peristalsis in the striated muscle part of the esophagus is dependent on central vagal pathways. It is mediated by sequential excitation of
Concluding Remarks
Understanding the basis for digestive tract functions is essential to understand dysfunctions in the functional gastrointestinal disorders. This article has discussed and critically assessed the normal physiology and pathophysiology, and the processes underlying symptom generation. From this careful review, the following recommendations for future research in this area emerge.
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Define new characteristics of wall function other than phasic and tonic contractions (eg, longitudinal muscle
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Conflicts of interest The authors disclose no conflicts.